If you query for local flash disks during creation of a virtual flash resource or Virtual SAN configuration, the ESXi host might not return a complete list of the local flash disks.
ESXi might not be able to automatically detect flash disks, or recognize them as local.
ESXi does not recognize certain devices as flash disks when their vendors do not support automatic flash disk detection. In other cases, some non-SATA SAS flash disks might not be detected as local. When disks are not recognized as local flash disks, they are excluded from the list of flash disks available for such features that require only local flash disks.
You might need to manually tag disks as flash disks or as local.
If ESXi does not automatically recognize its disks as flash disks, tag them as flash disk disks.
If ESXi does not detect flash disks as local, manually set them as local.